In past years, the automotive industry has provided spare tires for replacement of punctured or blown out tires while traveling. However, efforts have been made to eliminate the need for the spare tire by providing improved designs for tires. Specifically, efforts have been made to provide a stable and economical tire that can run with little or no pressure when, for example, the tire is flat. The term for the efforts has become known as “run flat tire” (RFT) technology. The RFT concept allows an operator to continue driving or rolling for an extended period of time without stopping to replace the tire or seeking emergency assistance. A tire can be repaired at a later, more convenient time.
One embodiment of an RFT wheel assembly includes a rim, a tire mounted on the rim, and a support sandwiched between an inner surface of the tire and an outer peripheral surface of a rim. The support allows the tire to deflect a limited amount so that the tire does not separate from the rim along each edge of the tire.
A synthetic material, such as a polymer, is typically used for the support. A challenge in manufacturing the support is to provide adequate structural integrity to have sufficient strength, so that outwardly directed centrifugal forces do not substantially deform the RFT support during rotational use. Further, the support needs to be able to support the weight of the vehicle on the tire, when the tire contacts the support as the tire rolls. The structural integrity is balanced with structural flexibility, in that the support is typically deformed slightly to insert the support into the tire prior to mounting the tire to the rim.
The process of producing an RFT support typically involves some type of molding. A mold for the support can include a narrow channel of about three millimeters (mm) in width that is formed about an inner or outer periphery of the mold. The polymer support can be reinforced to help maintain its structural integrity during adverse conditions by providing a reinforcement in the molding process. The reinforcement is placed in the channel prior to molding and the polymer typically flows therethrough to encapsulate the reinforcement into the molded RFT support.
To support cost effective production, the speed and efficiency in which the RFT reinforcement can be manufactured and placed into the mold to create an RFT support is important. Prior to the present invention, there did not appear to be a profitable production method of manufacturing RFT reinforcements that were suitable for quick placement.
Prior efforts have focused on using a mesh of reinforcement material, typically known as a woven “scrim” cloth, that is wound multiple times around a mandrel into a cylindrical shape and then cut and removed from the mandrel. The number of layers is at least partially determined by an amount of reinforcement resistance to deflection desired, as an indication of strength, with more layers providing more strength when other parameters are constant. The scrim cloth reinforcement, in multiple layers, is then “stuffed” into the mold channel and the polymer flowed into the mold.
However, use of standardized scrim cloth can lead to increased manufacturing complexities. For example, generally multiple layers of cloth are needed to form the RFT reinforcement. The layers need to be sufficiently coupled together, so that they do not delaminate. Further, the reinforcement insertion time can be relatively long, if the reinforcement is so flexible that it does not have a stable shape or a compact thickness for ease of insertion into the channel. Still further, molding material generally flows through openings in the reinforcement during production of the support. It is generally beneficial to align openings in the several layers of mesh, so that molding material can readily flow through the openings. Aligning the several layers of openings can add complexities to the process and tooling. Also, the flexible cloth-type of reinforcement is generally produced in individual units and adds cost to the support.
Other factors can also affect the production efficiency. Material, especially fibrous material, can have an expanded thickness called “loft,” where individual fibers can be spaced apart from adjacent fibers. Loft can cause difficulty in inserting the material into narrow mold cavities. Also, multiple layers of scrim cloth or other reinforcement material can add difficulties in inserting the multiple layers into the mold, if the layers are decoupled from each other or become delaminated during use.
Therefore, there remains a need for an improved RFT support reinforcement and RFT support, where the reinforcement can be readily inserted into a support mold and still be cost efficient to manufacture and where the manufactured product can be readily identified. A stable, relatively rigid reinforcement is needed to allow consistent placement of the reinforcement in an automated or manual process.